Assessment of the use of sediment fences for control of erosion and sediment phosphorus loss after potato harvesting on sloping land

In the 2010/11 trial the main fence comprised 70 m of entrenched fine mesh (0.25 mm) and coarser mesh (4 mm) fabric pinned to a contour fence near the base of the field. This retained an estimated 50.9 m3 (80.2 tonnes) of sediment, with weighted mean total P (TP) content of 0.09 % in the < 2 mm soil fraction. In the 2011/12 trial, the main 146 m fence was of intermediate mesh size (1.2 mm). The fence was partitioned into nine upslope plots, with 3 replicates of each of 3 cultivation methods: T1 (full grubbing - a light, tined cultivator), T2 (partial grubbing) and T3 (no grubbing). Average plot slopes ranged from 9.9 to 11.0 %. The amounts of TP accumulating as sediment at the fences were: 9.3 (sd = 7.8), 11.8 (sd = 10.2) and 25.7 (sd = 5.8) kg P/ha of upslope plot for the T1, T2 and T3 treatments respectively.